In an uplink channel in a cellular radio transmission system, when a transmission is performed by high power around the maximum transmission power in a signal format of a large PAPR (peak to acquire ratio), there occurs a large distortion by a transmission amplifier. As a result, the ACLR (adjacent carrier leakage ratio) to be considered in a radio system cannot be satisfied. To avoid the disadvantage, a device for reducing the maximum transmission power can be implemented in a cellular radio transmission system.
As a standardized radio communication system in a 3GPP (3rd generation partnership project) of an organization of standardization, HSUPA (high speed uplink packet access) radio communication system is well known. The radio communication system is an extended system of WCDMA (wideband code division multiple access) as a third generation mobile telephone radio access system similarly standardized by the 3GPP. In the HSUPA, with an increasing number of multiple codes, a system of reducing the above-mentioned maximum transmission power is implemented. In this case, as the reference quantity for control of the maximum transmission power, the quantity of cubic metric expressed by the following equation is defined.CM=CEIL{[20*log 10((v_norm3)rms)−20*log 10((v_norm_ref3)rms)]/k,0.5}  [equation 1]
In the equation 1, “v_norm” indicates a voltage value of a transmission signal. “rms” indicates a root mean square operation. “k” is a constant depending on the transmission format, and can be 1.85 or 1.56. “v_norm_ref” indicates a voltage value of a waveform of a reference signal of an AMR (adaptive multi-rate codec) of 12.2 kbps, and 20*log 10 (v_norm_ref 3) rms=1.52. The AMR is one of the audio coding systems of the WCDMA standardized by the 3GPP. The CEIL (x, p. 5) indicates a round-up operation in 0.5 units.
In the HSUPA, it is regulated that a terminal can reduce the maximum transmission power depending on the quantity of the CM. The CM is reference quantity required to satisfy the above-mentioned ACLR. The ACLR indicates a definite influence of the third order intermodulation distortion, and the third order intermodulation distortion is proportional to the cube of power. Then, the CM is obtained by the cube of power.
When the standard is adopted, the terminal calculates the maximum transmission power by considering the amount of reduction by the CM after the calculation of the CM, and performs a transmission with the transmission power reduced to the maximum transmission power when the transmission is to be performed with the power exceeding the maximum transmission power.
There is a control system performed without obtaining the CM and without changing the maximum transmission power. However, in this case, the cost of the transmission amplifier increases, and there is a necessity to raise the power allowed by the transmission amplifier.
When a CM operation is performed, it is necessary to obtain a transmission voltage value v_norm when a calculation is directly performed by the definition equation of the equation 1. However, with the configuration of a normal transmitter, a transmission is practically performed immediately after generating a transmission waveform. Therefore, the time to perform power control of the CM cannot be reserved after generating a transmission waveform.
Therefore, a conventional system is devised to first consider that the transmission data in digital communications is arranged at random unless the meaning of data is not taken into account, generate a pseudo-transmission waveform using a random signal while channel encoding (turbo-coding etc.) is being performed, and calculate the CM on the pseudo-transmission waveform.
However, in this conventional technology, a transmitter of a system different from a system for generating a practical transmission waveform is required, thereby doubling the scale of the circuit only for power control.
The following document of the prior art has been disclosed.    Patent Document 1: Japanese Laid-open Patent Publication No. 2004-208051